One of the many failures of secular worldviews is that they cannot account for the concept of a universal human dignity. Those who hold to these worldviews presuppose human dignity regardless. The question is that of origins and the nature of the human race.
Secular theories remove God from the equation and thereby remove man’s true identity as a special creature of God made in His image bearing a unique soul.
It is with the worldview of man being not only a special creature of God but a direct representative agent of God that we can expect the value of human life to fit in nicely. The Bible’s explanation of why murder is wrong is solely because man is God’s image (Genesis 9:6) and therefore as an image of God is inherently and infinitely valuable.
Secular theories on the other hand must account for the human dignity we all expect to be given when at core these theories teach man to be the product of time and chance acting on matter in an unguided universe with no objective meaning.
Man being a compilation of chemicals and only chemicals should not be expected to be given an inherent dignity or value above any other chemical compilations.
And yet the secular worldview is the most outspoken of the worldviews accusing the Christian religion as being responsible for the mistreatment of the humans whose dignity cannot be justified without relying on the very God they claim they can live without.
I find these internal inconsistencies of the secular worldview to be a testimony of the inadequacy of life without God both on a practical level and a philosophical level.